The machine is working great. No real issues, other than the lame iTunes HDCP issues. I was really looking forward to watching movies on here. Oh well.
Still running Yosemite, 10.10.5. I saw some earlier reports of issues with USB 3 and 10.11, so I haven't jumped ship. May not for a little while, as the machine generally performs fine. I do have 16GB of RAM on the way. I'm going to put it in the other RAM channel, as it's a 2x8 kit. I already have a 2x4 kit in. The ram is the same spec for spec, other than capacity. I contemplated maxing out to 32GB, but one that's overkill for my usage, and two not worth the cost. I figured I'd make an in between leap to 24GB. Should be interesting.
After that, I am in serious need of a larger OS SSD, likely a 500GB eventually, and maybe a graphics card. I'm thinking a 660ti would be a good bet, as I could get it used at a decent price and use Apple drivers with it. After that, CPU cooler and some more internal data storage.
The only issues I have these days lies in software. Sometimes Finder will do some weird BS where I can't drag and drop files out of stacks in my dock. Killing Finder and Dock don't help. A reboot solved it. Aside from that and a random instant logout I had the other day, all is well. Overall, far better than my macbook pro.